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Nico67

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Simulate Phase noise DLL
Aug 13^th, 2004, 5:21am

Hello, I want to simulate the phase noise of my DLL.

In first, I use the simulation PSS and Pnoise with my VCDL. I obtain a result in dBc/Hz, and with some calculations I obtain the phase noise in ps.

But I don't sure that the result is just because the jitter is approximately 0.15ps. I think that I not use a good transformation for pass dbc/Hz to ps.

If you can explian the calculation for this transformation

Thank

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Jitter Man Community Member Offline Am I? Or am I so sane that u just blew your mind? Posts: 50	Re: Simulate Phase noise DLL Reply #1 - Aug 13^th, 2004, 7:39am To characterize the jitter of a VCDL you would use the same procedure you would for a PFD, which is described in Modeling jitter in PLL-based frequency synthesizers at www.designers-guide.com/Analysis. Jitter Man
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Nico67

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Re: Simulate Phase noise DLL
Reply #2 - Aug 13^th, 2004, 7:54am

Thanks, jitter man

but I have some questions:

I use the method describe in this guide, and I obtain a curve for the phase noise in dBc/Hz.

I have a clock at 62.5MHz and for the simulation, i want to simulate the phase noise of the buffers.

I obtain, for example -165dbC at 100KHz eg 0.001ps that I can't be exact.

1. How choose the value of delta f ?
2.Why don't integrated the curve of the phase noise?

Thanks

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Jitter Man

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Am I? Or am I so
sane that u just
blew your mind?

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Re: Simulate Phase noise DLL
Reply #3 - Aug 13^th, 2004, 10:58am

Sorry, I misled you a bit. You should not follow the procedure for extracting jitter of the PFD, which has an analog output, you should follow the procedure for extracting jitter of a frequency divider, a purely digital circuit. This is section 4.1 in the given reference. Notice that it indicates you should integrate the noise density from -f₀/2 to f₀/2.

Jitter Man

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Nico67

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Re: Simulate Phase noise DLL
Reply #4 - Aug 16^th, 2004, 12:50am

Thanks

I simulate with Cadence RF Pnoise

In sweeptype I use relative and in Sweep range I use
min 0 max Fo/2 . Are you ok?

Input source none because I want simulate the contribution of noise of the buffers in my VCDL.

In positive output node i use a output of my VCDL.

To this output I see the contribution of all the buffers or just the buffer corresponding to the node?

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Nico67 Junior Member Offline Posts: 19	Re: Simulate Phase noise DLL Reply #5 - Aug 17^th, 2004, 6:48am Please I need help to calculate the phase noise in ps. When I have the curve in dBc/Hz I don't know how to transform this phase noise to ps. In the analisys , you use a c=L(f)*deltaf^2/fo^2 but how choose the value of the deltaf?
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Frank Wiedmann Community Fellow Offline Posts: 677 Munich, Germany	Re: Simulate Phase noise DLL Reply #6 - Aug 17^th, 2004, 8:35am You should probably use the strobed noise analysis of SpectreRF. See http://www.designers-guide.com/Analysis/PLLnoise+jitter.pdf, in particular section 9.
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Nico67

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Re: Simulate Phase noise DLL
Reply #7 - Aug 17^th, 2004, 10:28am

I have read all the analysis but I don't understand how choose the delta(f) in the formule.

I make the simulation Pnoise and I obtain the curve Phqse Noise dbc/Hz.

In the example of the analysis you explain that you obtain -95dBc at 100KHz. But I don't know that you choos e the 100KHz.

In other analysis they integre the curve from fc to 10MHz, and the result is not the same.

Thanks for your informations

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Frank Wiedmann Community Fellow Offline Posts: 677 Munich, Germany	Re: Simulate Phase noise DLL Reply #8 - Aug 17^th, 2004, 11:46pm The rule how to choose delta(f) is given immediately after equation (77) in the paper I mentioned. However, this should not bother you at all because a DLL is not an autonomous system. There is no delta(f) in the equations in section 9.
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Nico67 Junior Member Offline Posts: 19	Re: Simulate Phase noise DLL Reply #9 - Aug 18^th, 2004, 2:38am Thank Frank, The phase noise of the buffers is in the Jitter type synchronous and I need use the period jitter corresponding for a PLL to the PFD. It is just ?
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Frank Wiedmann Community Fellow Offline Posts: 677 Munich, Germany	Re: Simulate Phase noise DLL Reply #10 - Aug 18^th, 2004, 4:03am Use the same procedure as for the divider (as already mentioned by Jitter Man), see section 9.1.1.
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Nico67 Junior Member Offline Posts: 19	Re: Simulate Phase noise DLL Reply #11 - Aug 18^th, 2004, 6:38am Ok How determine dv/dt with the PSS simulation ? Thanls
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Frank Wiedmann Community Fellow Offline Posts: 677 Munich, Germany	Re: Simulate Phase noise DLL Reply #12 - Aug 18^th, 2004, 6:51am You can use the calculator functions deriv() to get the derivative and value() to pick the correct t_c.
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Nico67 Junior Member Offline Posts: 19	Re: Simulate Phase noise DLL Reply #13 - Aug 18^th, 2004, 7:32am But with PSS simulation I don't have a curve , I have curve with the harmonic range.
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Nico67 Junior Member Offline Posts: 19	Re: Simulate Phase noise DLL Reply #14 - Aug 18^th, 2004, 7:33am Ok I have find in sweep I use time and not spectrum
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